Melena caused by Gastric Ulceration Atlas of swine pathology pig333, pig to pork community MALENA: Melena is the medical term for black, tarry stools caused by the presence of digested blood. It typically indicates bleeding in the upper gastrointestinal (GI) tract, such as the: Stomach Duodenum Retroflexions.com The Rectal Bleeding Rainbow What does your poop colour indicate? Pay attention. There's a lot to be learned by the colour and consistency of your stools, as well as the frequency and how easily passed Poop color: What does it mean?